Evidence has accumulated from human and animal studies that electrical stimulation of the cerebellum has a suppressive effect on epileptic seizures. Although the evidence is inconsistent, there appears to be sufficient promise in this mode of therapy to warrant further intensive study. Our own work in the laboratory in the past two years suggests that cerebellar stimulation is ineffective in arresting individual seizures. This applies both to electrically-induced and to spontaneously occuring alumina-type focal seizures in awake Rhesus monkeys. We observed, however, that chronic stimulation appears to reduce overall frequency of occurence of seizures. Little attention in previous studies has been given to the question of chronic intermittent stimulation and the possibility of cumulative beneficial effect in suppressing the tendency to seizures. Accordingly, in the present protocol, we have adopted a research strategy involving the use of a chronic animal model of epilepsy. The experiments are intended to determine the effect of chronic intermittent electrical stimulation (with variations in locus and duration of stimulation) of cerebellar cortex on the frequency of occurrence of spontaneous, focal alumina seizures in awake Rhesus monkeys. On the basis of such data, it may be possible to determine whether full-scale systematic studies in humans would be justified.